This is the first time I've tackled plumbing. I've done everything else around the house, just not plumbing. I may need to do this job to save some money. I've attached some images here for review. This is my first attempt, so go easy on me. Thank you in advance for all advice and direction, it's much appreciated!!

First image shows the old tub drain. I've highlighted in red, what I beleive I should remove. I'm proposing putting a Y fitting in it's place for the double vanity and new shower to use the existing drain.

Second image shows potential drain and venting for the double vanity.

Third image shows the run from the Y to the shower drain.

Does anyone see potential issues here? Will this work?

I've yet to settle on the supply runs, I'm trying to figure out if I really need a pressure loop, did I say that correctly? I'd like a total of 4 water sources, 2 shower heads so the Mrs. and I can shower at same time, a hand held, and a rain head. I don't think I have enough GPM to feed all of this at the same time, it appears that I only have 1/2" pipe in the bathroom and not 3/4. I figure if I never have more than 2 maybe 3 shower heads going at the same time, maybe I'd be ok? Thoughts on this?

Once I feel like I have the drain and vent correctly planned, I'll draw out some pictures for supply lines and post for comment.

Again, thanks in advance for any help/advice you can give me. If you want more pictures, just let me know.

It looks like you have several issues to deal with. Vents for the shower and toilet to name at least two of them. You really should get a plumber involved because there are a number of other things that have to be done correctly to pass inspection.

If that is a 2" pipe in the background going up the wall, then your tub drain appears to be smaller which means it could be 1 1/2" pipe, in which case it cannot be used for ANYTHING except a single sink drain. The majority of plumbers who do things to the minimum code level would have used a 1 1/2" drain for the tub.

If the pipe is a 2", then you can drain the two lavs and the shower.
The lavs can be plumbed using a fixture fitting and combined. The shower needs to be vented correctly; not sure where the shower is from the pictures.
Two shower heads from 1/2" should be fine.